This invention relates to a control signal generator for generating control signals for an internal combustion engine. More particularly, it relates to a control signal generator which can generate signals for use in controlling both the ignition timing and the fuel injection of the engine.
In order for an internal combustion engine to operate optimally, fuel injection and ignition must take place at prescribed rotational angles of the crankshaft, i.e., when each piston of the engine is at a prescribed position with respect to top dead center. For this reason, an engine is equipped with a signal generator having a rotational position sensor which senses the rotational angle of the crankshaft of the engine. One common type of position sensor is in the form of a rotating plate mounted on a rotating shaft (such as the distributor shaft) which rotates in synchrony with the crankshaft of the engine. The rotating plate has projections formed thereon which can be detected by a transducer disposed in the vicinity of the rotating plate. The transducer generates electrical signals as the projections pass by it. The projections, which equal the number of cylinders, are disposed so as to correspond to prescribed rotational angles of the crankshaft and thus to prescribed positions of each piston.
In addition to knowing when the crankshaft reaches a prescribed rotational position for each cylinder, in engines in which the cylinders are individually controlled, it is necessary to be able to identify each cylinder. A signal generator of an engine which performs individual control of the cylinders is therefore equipped with second position sensor for sensing when the crankshaft rotational angle is such that the piston of a specific reference cylinder is in a prescribed position. The second position sensor is similar in structure to the above-described position sensor and usually consists of a rotating plate having only a single projection and a magnetic transducer which generates an output signal when the projection passes by it. By using the outputs of the two position sensors in conjunction, it can be determined which cylinder of an engine is firing at any given time.
Thus, a conventional control signal generator for an engine is frequently equipped with two different position sensors. However, as position sensors are expensive and each sensor requires a separate interface circuit for connection to an engine controller, the use of two separate position sensors is uneconomical. It is also disadvantageous from the standpoint of space utilization in an engine.